Sensitive Detection of Copper (II) Ions in Aqueous Solutions Using Thioglycolic Acid-Capped Ce-Doped ZnS Nanoparticles Based Fluorescent Probe

Abstract

The synthesis of fluorescent water dispersible thioglycolic acid (TGA)-capped Ce-doped ZnS nanoparticles (coded as Ce-ZnS@TGA) was carried out using environment friendly co-precipitation approach. The as-synthesized nanoparticles were characterized using powder X-ray diffraction (PXRD), HRTEM, Energy Dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, and fluorescence spectroscopy. The Ce-ZnS@TGA probe was found to show significant enhancement on addition of urea. Further, the fluorescence intensity of the Ce-ZnS@TGA-urea complex was quenched on addition of Cu²⁺ ions. The Ce-ZnS@TGA-urea complex was used as a fluorescence probe for detection of Cu²⁺ ions in aqueous samples. The quenching of the fluorescence intensity of Ce-ZnS@TGA-urea was possibly due to non-radiative recombination as Cu²⁺ions act as electron trapping center. The LODs for detection of urea and Cu²⁺ ions was determined to be 2.3mM and 26.6 µΜ respectively. The factors affecting the detection of Cu²⁺ ions such as presence of other metal ions were also investigated and the optimum pH value for the sensor was evaluated. The proposed method was also employed to detect trace Cu²⁺concentrations in real water samples with satisfactory results.

Keywords: Ce doped; Detection of copper; Fluorescence quenching; Fluorescent probe; ZnS nanoparticles.